my @array = qw/some stuff in here/;



   #instead of:

my @matches = grep { /^s/ } @array;

   #which would give you ("some","stuff");



   #you could try something like this:

my @indices = grep { $array[ $_ ] =~ /^s/ } 0..$#array;

   #which would give you (0,1), which are the indices of the array you want.
   #and then to get matches, you can still do something like:

my @matches = @array[ @indices ];